Tomography, the three dimensional imaging of living organisms originally utilized X-ray techniques to achieve desired goals. Therefore, due to the radiation hazards created by the large amounts of X-ray radiation required, this important, non-invasive tool has not been used to its fullest potential. However, the evolution of nuclear magnetic resonance (NMR) spectrometers into imaging systems has provided a means for imaging living organisms without the hazardous radiation of X-ray systems and the development of compact and inexpensive computer systems through integrated circuit techniques has provided the basic technological tools from which a safe, graphic system may be created.
NMR imaging systems have been developed by numerous organizations and comprehensive papers on the subject have been published, see for instance "Proceedings of the IEE", Vol. 71, No. 3, which is devoted exclusively to technical papers on computerized tomography, which includes NMR imaging. At the present time, several commercial firms (e.g. Elscint, Siemens and Diasonics) offer NMR imaging systems.
Even though the technology is presently available, NMR imaging systems are not readily available due to their high initial and operating costs. Initial capital outlays can be in the range of several millions of dollars for an NMR system. One factor leading to a high initial and maintenance cost is that the main magnets are superconductive and require liquid helium based refrigeration systems. Also, system operation and maintenance require highly skilled personnel. Many organizations, including the U.S. government, are attempting to keep medical costs under control. There is thus great difficulty in acquiring such systems, even in spite of the benefits to the community they would serve through their fantastic imaging power. Therefore, measures which will reduce the operating cost or increase the productivity of NMR imaging systems are needed.